Air to ground communication system with separate control and traffic channels

ABSTRACT

A base station within a network for providing ATG wireless communication in various cells may include an antenna array defining a plurality of wedge shaped sectors having respective widths defined in azimuth, and a beamforming control module. The beamforming control module may be configured to communicate with the antenna array via a first RF chain to perform beamforming defining traffic channel beams having a first width, and a second RF chain to perform beamforming defining control channel beams having a second width. The second width may be greater than the first width.

TECHNICAL FIELD

Example embodiments generally relate to air-to-ground (ATG) wirelesscommunications and, more particularly, relate to employing beamformingfor antennas used for ATG communications.

BACKGROUND

High speed data communications and the devices that enable suchcommunications have become ubiquitous in modern society. These devicesmake many users capable of maintaining nearly continuous connectivity tothe Internet and other communication networks. Although these high speeddata connections are available through telephone lines, cable modems orother such devices that have a physical wired connection, wirelessconnections have revolutionized our ability to stay connected withoutsacrificing mobility.

However, in spite of the familiarity that people have with remainingcontinuously connected to networks while on the ground, people generallyunderstand that easy and/or cheap connectivity will tend to stop once anaircraft is boarded. Aviation platforms have still not become easily andcheaply connected to communication networks, at least for the passengersonboard. Attempts to stay connected in the air are typically costly andhave bandwidth limitations or high latency problems. Moreover,passengers willing to deal with the expense and issues presented byaircraft communication capabilities are often limited to very specificcommunication modes that are supported by the rigid communicationarchitecture provided on the aircraft.

Conventional ground based wireless communications systems use verticalantennas to provide coverage for device connectivity concentrated nearthe ground. However, aircraft operate in three dimensional space thatextends far above the ground. Thus, it can be appreciated thatsignificant changes would be needed to be able to provide threedimensional coverage for aircraft up to cruising altitudes as high as45,000 ft.

In typical wireless technologies, logical channels are formed for datacarried over the radio interface. The logical channels define what typeof information is transmitted over the air such that both data andsignaling messages are carried on the logical channels. The logicalchannels may include control channels and traffic channels. The controlchannels carry control plane information while the traffic channelscarry user-plane data. In a terrestrial wireless communicationenvironment, control and traffic beams are generated in the context of asingle RF chain and feed because the specific location of users to beserved is generally unknown so equally wide beams are generally neededfor both. However, the ATG context presents a different situationentirely insofar as it may be possible to know the location of the usersto be served. Thus, a different structure and approach to beam formingmay be possible.

BRIEF SUMMARY OF SOME EXAMPLES

The continuous advancement of wireless technologies offers newopportunities to provide wireless coverage for aircraft using antennaswith unique beamforming capabilities installed at ground sites.

In one example embodiment, a network for providing air-to-ground (ATG)wireless communication in various cells is provided. The networkincludes a first base station having a first antenna array defining aplurality of first sectors having respective widths defined in azimuth,and a second base station having a second antenna array defining aplurality of second sectors having respective widths defined in azimuth.The first base station and the second base station are disposed offsetfrom each other along a first direction. Each of the first and secondbase stations includes a beamforming control module configured tocommunicate with the first and second antenna arrays, respectively, viaa first RF chain to perform beamforming defining traffic channel beamshaving a first width, and a second RF chain to perform beamformingdefining control channel beams having a second width. The second widthbeing greater than the first width.

In another example embodiment, a base station within a network forproviding ATG wireless communication in various cells is provided. Thebase station may include an antenna array defining a plurality of wedgeshaped sectors having respective widths defined in azimuth, and abeamforming control module. The beamforming control module may beconfigured to communicate with the antenna array via a first RF chain toperform beamforming defining traffic channel beams having a first width,and a second RF chain to perform beamforming defining control channelbeams having a second width. The second width may be greater than thefirst width.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 illustrates an aircraft moving through the coverage areas ofdifferent base stations over time in accordance with an exampleembodiment;

FIG. 2 illustrates a block diagram of a system for employing positionalinformation for assisting with beamforming in accordance with an exampleembodiment;

FIG. 3 illustrates control circuitry that may be employed to assist inusing positional information for assisting with beamforming at theremote radio head according to an example embodiment; and

FIG. 4 illustrates a perspective view of coverage areas generated by abase station of an example embodiment.

DETAILED DESCRIPTION

Some example embodiments now will be described more fully hereinafterwith reference to the accompanying drawings, in which some, but not allexample embodiments are shown. Indeed, the examples described andpictured herein should not be construed as being limiting as to thescope, applicability or configuration of the present disclosure. Rather,these example embodiments are provided so that this disclosure willsatisfy applicable legal requirements. Like reference numerals refer tolike elements throughout. Furthermore, as used herein, the term “or” isto be interpreted as a logical operator that results in true wheneverone or more of its operands are true. As used herein, operable couplingshould be understood to relate to direct or indirect connection that, ineither case, enables functional interconnection of components that areoperably coupled to each other.

In some example embodiments, a plurality of antennas at a base stationcan form individual sectors (in azimuth) that can be combined to achievesemicircular (or circular) coverage areas around the base station. Thesectors can also be defined between two elevation angles to define awedge shaped coverage area or cell that extends away from the basestation between the two elevation angles. Within each sector, aplurality of directional beams may be formed, and selection of specificones of the directional beams can result in effectively enablingsteering of the beams in both azimuth and elevation within the sector byselecting respective directional beams in sequence. The directionalbeams also have azimuth and elevation widths that define the size of thedirectional beams. Thus, beams can be swept in azimuth at a constantelevation angle within a respective sector to define the curved surfaceof a portion of a cone having its apex at the base station. Of note, thecurved surface may technically have a wedge shape as well since itextends between elevation angles defining the height of the steerablebeam. Considering multiple sectors, a beam could effectively be swept orsteered around the base station (by selecting corresponding directionalbeams) at the same elevation angle to define the cone shape (or portionthereof depending on how many sectors the beam was swept through). Thecone shape defined would generally have a radius much longer than theheight of the cone (e.g., nearly the length of the sides of the coneshape). Since the beams are effectively steerable in elevation as well,a concentric curved surface can also be swept at different elevationangles over the range of azimuths within one or more sectors to defineslightly different and concentric cone shapes (or portions thereof).Thus, the steering capability may allow directional beams to beeffectively “steered” toward a moving aircraft to follow the aircraft'smovement. This, of course, requires some knowledge of the location ofthe aircraft, which is knowledge that is generally not needed oremployed in the terrestrial context.

Additionally, some example embodiments may employ separate RF chains andfeeds for the antenna structures of the ground stations. Thus, forexample, at the logical layer, separate control beams and traffic beamscan be generated using a single antenna structure. The control beams andthe traffic beams can be generated to have different beamcharacteristics (e.g., different widths in azimuth and/or elevation). Insome cases, for example, the traffic beams can be narrower, and thecontrol beams can be wider. The ability to know something about target(e.g., aircraft) location and provide different width control andtraffic beams may enable a single antenna structure to functionallyoperate as two antennas. One such functional antenna may have widerdirectional beams than the other functional antenna.

Accordingly, some example embodiments described herein may providearchitectures for improved air-to-ground (ATG) wireless communicationperformance. In this regard, some example embodiments may provide forbase stations having antenna structures that facilitate providingwireless communication coverage via beamforming of separate control andtraffic beams so that different sizes of such beams can be provided.Furthermore, example embodiments may enable the beams (of differentsizes) to be formed and selected for effective steering in vertical andhorizontal directions with sufficient elevation to communicate withaircraft at high elevations. A base station can provide a wedge shapedcoverage area in which steerable beams can be steered to achievecoverage at a predetermined altitude within a predetermined distancefrom the base station to facilitate ATG wireless communications. Thewedge shaped coverage area can be substantially semicircular (orcircular) in the horizontal plane, and can be provided by multipleantennas each providing a wedge shaped sector over a portion of thesemicircular azimuth. The base stations can be deployed as substantiallyaligned in a first direction while offset in a second direction. Forexample, the base stations can also be deployed in the first directionat a first distance to provide coverage overlapping in elevation toachieve coverage over the predetermined altitude, and within a seconddistance in the second direction based on an achievable coverage areadistance of the sectors. The steerable beams may be steerable in bothazimuth and elevation angle to define cell coverage areas that aredefined between elevation angle limits that are centered at and extendaway from the base stations aimed just above the horizon. By providingthe cells to extend toward the horizon, the coverage area above anyparticular base station may not be provided by that base station.Instead, an adjacent base station may provide coverage above eachindividual base station in order to reduce the possibility ofinterference from ground based emitters since the aircraft can look tothe horizon for service instead of directly below, where the majority ofinterferers within range would be expected to be located.

FIG. 1 illustrates a conceptual view of an aircraft moving through acoverage zone of different base stations to illustrate an exampleembodiment. As can be seen in FIG. 1, an aircraft 100 may be incommunication with a first base station (BS) 110 at time t₀ via a firstwireless communication link 120. The aircraft 100 may therefore includewireless communication equipment onboard that enables the aircraft 100to communicate with the first BS 110, and the first BS 110 may alsoinclude wireless communication equipment enabling communication with theaircraft 100. As will be discussed in greater detail below, the wirelesscommunication equipment at each end may include radio hardware and/orsoftware for processing wireless signals received at correspondingantenna arrays that are provided at each respective device incommunication with their respective radios. Moreover, the wirelesscommunication equipment of example embodiments may be configured toemploy beamforming techniques to utilize directive focusing, steering,and/or formation of beams using the antenna arrays. Accordingly, for thepurposes of this discussion, it should be assumed that the firstwireless communication link 120 between the aircraft 100 and the firstBS 110 may be formed using at least one link established viabeamforming. In other words, either the first BS 110 or the aircraft100, or both, may include radio control circuitry capable of employingbeamforming techniques for establishment of the first wirelesscommunication link 120.

A second BS 130, which may have similar performance and functionalcharacteristics to those of the first BS 110, may be locatedgeographically such that, for the current track of the aircraft 100, thesecond BS 130 is a candidate for handover of the aircraft 100 tomaintain a continuous and uninterrupted communication link between theaircraft 100 and ground-based base stations of an ATG wirelesscommunication network at time t₁. It may be helpful for the second BS130 to be aware of the approach of the aircraft 100 so that the secondBS 130 can employ beamforming techniques to direct/select a beam aimedtoward the expected location of the aircraft 100. Additionally oralternatively, it may be helpful for the aircraft 100 to be aware of theexistence and location of the second BS 130 so that the wirelesscommunication equipment on the aircraft 100 may employ beamformingtechniques to direct a beam toward the second BS 130. Thus, at least oneof the second BS 130 or the wireless communication equipment on theaircraft 100 may employ beamforming techniques assisted by knowledge ofposition information to facilitate establishment of a second wirelesscommunication link 140 between the wireless communication equipment onthe aircraft 100 and the second BS 130. Thereafter, by time t₂, thefirst communication link 120 may be dropped and the aircraft 100 mayonly be served by the second BS 130 via the second wirelesscommunication link 140. In some cases, the handover between the first BS110 and the second BS 130 may be a hard handoff managed from the groundside of the ATG wireless communication network.

In accordance with an example embodiment, a beamforming control modulemay be provided that employs knowledge of position information regardinga receiving station on an aircraft or ground stations to assist inapplication of beamforming techniques. Of note, beamforming techniquesin accordance with some example embodiments may include selection of oneof a plurality of fixed beams, where the selected fixed beam is aimed atthe desired location. Thus, beam steering or beamforming should beunderstood to also encompass selection of a fixed beam having a desiredorientation or projection pattern (e.g., beam selection). In any case,one or more instances of the beamforming control module of an exampleembodiment may be physically located at any (or all) of a number ofdifferent locations within an ATG communication network. FIG. 2illustrates a functional block diagram of an ATG communication networkthat may employ an example embodiment of such a beamforming controlmodule at the remote radio head proximate to the antenna array of a basestation.

As shown in FIG. 2, the first BS 110 and second BS 130 may each be basestations of an ATG network 200. The ATG network 200 may further includeother BSs 210, and each of the BSs may be in communication with the ATGnetwork 200 via a gateway (GTW) device 220. The ATG network 200 mayfurther be in communication with a wide area network such as theInternet 230 or other communication networks. In some embodiments, theATG network 200 may include or otherwise be coupled to a packet-switchedcore network.

In an example embodiment, the ATG network 200 may include a networkcontroller 240 that may include, for example, switching functionality.Thus, for example, the network controller 240 may be configured tohandle routing calls to and from the aircraft 100 (or to communicationequipment on the aircraft 100) and/or handle other data or communicationtransfers between the communication equipment on the aircraft 100 andthe ATG network 200. In some embodiments, the network controller 240 mayfunction to provide a connection to landline trunks when thecommunication equipment on the aircraft 100 is involved in a call. Inaddition, the network controller 240 may be configured for controllingthe forwarding of messages and/or data to and from the aircraft 100 or amobile terminal on the aircraft 100, and may also control the forwardingof messages for the base stations. It should be noted that although thenetwork controller 240 is shown in the system of FIG. 2, the networkcontroller 240 is merely an exemplary network device and exampleembodiments are not limited to use in a network employing the networkcontroller 240.

The network controller 240 may be coupled to a data network, such as alocal area network (LAN), a metropolitan area network (MAN), and/or awide area network (WAN) (e.g., the Internet 230) and may be directly orindirectly coupled to the data network. In turn, devices such asprocessing elements (e.g., personal computers, laptop computers,smartphones, server computers or the like) can be coupled to thecommunication equipment on the aircraft 100 via the Internet 230.

Although not every element of every possible embodiment of the ATGnetwork 200 is shown and described herein, it should be appreciated thatthe communication equipment on the aircraft 100 may be coupled to one ormore of any of a number of different networks through the ATG network200. In this regard, the network(s) can be capable of supportingcommunication in accordance with any one or more of a number offirst-generation (1G), second-generation (2G), third-generation (3G),fourth-generation (4G) and/or future mobile communication protocols orthe like. In some cases, the communication supported may employcommunication links defined using unlicensed band frequencies such as2.4 GHz or 5.8 GHz. However, licensed band communication, such ascommunication in a frequency band dedicated to ATG wirelesscommunication, may also be supported.

As indicated above, a beamforming control module may be employed onwireless communication equipment at either or both of the network sideor the aircraft side in example embodiments. Thus, in some embodiments,the beamforming control module may be implemented in a receiving stationon the aircraft (e.g., a passenger device or device associated with theaircraft's communication system). In some embodiments, the beamformingcontrol module may be implemented in the network controller 240, at oneor more of the base stations, or at some other network side entity.Moreover, in some example embodiments, beamforming may be accomplishedby providing location/position information at a remote radio head (RRH)of the base stations to enable antenna beamforming as described herein.

FIG. 3 illustrates the architecture of a base station (e.g., BS 110, BS130 or BS 210) employing a beamforming control module 300 in accordancewith an example embodiment. As shown in FIG. 3, the base station mayinclude an antenna array 250, a remote radio head (RRH) 260 and a baseunit 270. The base unit 270 may include power supply, backhaulconnectivity, and various signal processing and other processingcapabilities typically associated with a base station. In a typicalsituation, the base unit 270 may be operably coupled to the antennaarray 250 to interact with the antenna array 250 to receive inboundsignals therefrom and to direct the antenna array 250 relative to beamformation for creating communication links with in-flight aircraft(e.g., aircraft 100). However, in a typical situation, the base stationmay also include a tower or mast that can be relatively high. Thus, tothe extent that the transmitter is located in the base unit 270, hightransmission capacity would need to be provided between the base unit270 and the antenna array 250 via cabling extending as far as severalhundred feet. To minimize the cable lengths, the RRH 260 may beprovided.

The RRH 260 may include RF circuitry and analog-to-digital and/ordigital-to-analog converters. The RRH 260 may also include up/downconverters and have operational and management capabilities (asdiscussed below in greater detail). In some cases, the RRH 260 furtherincludes a high-frequency transmitter, and the RRH 260 is providedproximate to the antenna array 250. Thus, the length of high-frequencytransmission lines between the RRH 260 and the antenna array 250 can berelatively short. This allows increased efficiency of the base stationand reduces the cost associated with expensive and long cables.Meanwhile, a power cable and a data cable (and a control cable ifneeded) can be provided to operably couple the RRH 260 and the base unit270. In some cases, the power cable and data cable can be combined intoa single hybrid cable.

In an example embodiment, the beamforming control module 300 may beembodied in processing circuitry at the RRH 260. However, other exampleembodiments may not employ the RRH 260 at all, and the beamformingcontrol module 300 could be instantiated at the base unit 270 in suchcases. In any case, the beamforming control module 300 may use locationinformation (or position information) indicative of the location of theaircraft 100 (in relative or absolute terms) to direct the antenna array250 to form a beam directed toward the aircraft 250. As such, in caseswhere the RRH 260 is employed, the beamforming control module 300 mayinteract with the antenna array 250 via the RRH 260 so that the RRH 260is informed as to where the aircraft 100 is located to allow the RRH 260to tell the antenna array 250 which specific beam to form to reach theaircraft 100. Moreover, the beamforming control module 300 may beconfigured to direct formation of the beams to have a limited width inboth azimuth and elevation angle, and the beams may be steered in bothazimuth and elevation.

In an example embodiment, the beamforming control module 300 may beconfigured to direct different sized beams to be formed dependent uponwhether the beam to be formed is a traffic beam or a control beam. Thus,the base station may include at least two RF chains and correspondingfeeds. A first RF chain 325 may be provided to the antenna array 250 todirect formation of traffic channel beams 340. Meanwhile, a second RFchain 335 may be provided to the antenna array 250 to direct formationof control channel beams 350. As can be appreciated from FIG. 3, thecontrol channel beams 350 may be generally wider than the trafficchannel beams 340. Given that the location of the target (e.g., theaircraft 100) is known, the control channel beams 350 can be morefocused than it would otherwise be in a terrestrial system. Moreover,the traffic channel beams 340 can be even narrower still. Accordingly,the antenna array 250 may be configured to functionally act as twodifferent antennas, one of which generates wider control channel beams350, and the other of which generates narrower traffic channel beams340.

One challenge that may be provided by example embodiments is to ensurethe control channel provides sufficient coverage to its entirecorresponding sector. Wider beams (such as a wider control channel beam)typically have less gain that narrower beams (e.g., focused trafficchannel beams). The control channel therefore usually uses a more robustmodulation and coding level to help make up the difference. However, insome cases the use of more robust modulation and coding level may not besufficient to allow the control channel coverage to equal the coveragerange of the focused traffic channel.

Since example embodiments provide a separate control channel RF chainfrom the traffic channel RF chain, some example embodiments may furtherenable a split of the control channel RF feed so that the RF feed can besent to more than one antenna, with each antenna pointing into adifferent azimuth with a more narrow beamwidth. As a result, forexample, instead of feeding one RF chain into one antenna with a 60degree beamwidth, example embodiments may enable a split of the controlchannel signal into two or more RF feeds and send the signal into two 30degree beamwidth antennas, or three 20 degree beamwidth antennas, etc.Example embodiments may therefore provide a greater antenna gain to thecontrol channel by further segmenting the RF feed chain for the controlchannel.

Normally, splitting of the control channel would not make sense. In thisregard, if the power amplifier puts out a certain power level, thesplitter to go to the two antennas would introduce a 3 dB loss. Thus,given that the more narrow beamwidth of the antenna would result in a 3dB gain, the gains and losses of the system would net a zero sum gain.However, the example embodiment would realize a net gain in cases wherethe spectrum licensing rules limit the conducted power into a particularantenna. In such cases, by employing an example embodiment with split RFchains, a net gain can be achieved.

Example embodiments may therefore provide intelligence associated withbeamforming that can communicate with an antenna assembly over twoseparate RF chains, one for control beams and one for traffic beams, sothat the provision of amplitude and phase information associated withbeamforming can be accomplished with one physical structure, but enablethe physical structure to act as two functional antennas. Thebeamforming control module 300 may include processing circuitry 310configured to provide control outputs for generation of beams of twodistinct sizes at the antenna array 250 disposed the base station basedon processing of various input information. The processing circuitry 310may be configured to perform data processing, control function executionand/or other processing and management services according to an exampleembodiment. In some embodiments, the processing circuitry 310 may beembodied as a chip or chip set. In other words, the processing circuitry310 may comprise one or more physical packages (e.g., chips) includingmaterials, components and/or wires on a structural assembly (e.g., abaseboard). The structural assembly may provide physical strength,conservation of size, and/or limitation of electrical interaction forcomponent circuitry included thereon. The processing circuitry 310 maytherefore, in some cases, be configured to implement an embodiment ofthe present invention on a single chip or as a single “system on achip.” As such, in some cases, a chip or chipset may constitute meansfor performing one or more operations for providing the functionalitiesdescribed herein.

In an example embodiment, the processing circuitry 310 may include oneor more instances of a processor 312 and memory 314 that may be incommunication with or otherwise control a device interface 320. As such,the processing circuitry 310 may be embodied as a circuit chip (e.g., anintegrated circuit chip) configured (e.g., with hardware, software or acombination of hardware and software) to perform operations describedherein. However, in some embodiments, the processing circuitry 310 maybe embodied as a portion of an on-board computer. In some embodiments,the processing circuitry 310 may communicate with various components,entities and/or sensors of the ATG network 200.

The device interface 320 may include one or more interface mechanismsfor enabling communication with other devices (e.g., modules, entities,sensors and/or other components of the base station). In some cases, thedevice interface 320 may be any means such as a device or circuitryembodied in either hardware, or a combination of hardware and softwarethat is configured to receive and/or transmit data from/to modules,entities, sensors and/or other components of the base station that arein communication with the processing circuitry 310.

The processor 312 may be embodied in a number of different ways. Forexample, the processor 312 may be embodied as various processing meanssuch as one or more of a microprocessor or other processing element, acoprocessor, a controller or various other computing or processingdevices including integrated circuits such as, for example, an ASIC(application specific integrated circuit), an FPGA (field programmablegate array), or the like. In an example embodiment, the processor 312may be configured to execute instructions stored in the memory 314 orotherwise accessible to the processor 312. As such, whether configuredby hardware or by a combination of hardware and software, the processor312 may represent an entity (e.g., physically embodied in circuitry—inthe form of processing circuitry 310) capable of performing operationsaccording to example embodiments while configured accordingly. Thus, forexample, when the processor 312 is embodied as an ASIC, FPGA or thelike, the processor 312 may be specifically configured hardware forconducting the operations described herein. Alternatively, as anotherexample, when the processor 312 is embodied as an executor of softwareinstructions, the instructions may specifically configure the processor312 to perform the operations described herein.

In an example embodiment, the processor 312 (or the processing circuitry310) may be embodied as, include or otherwise control the operation ofthe beamforming control module 300 based on inputs received by theprocessing circuitry 310 responsive to receipt of position informationassociated with various locations or relative positions of thecommunicating elements of the network. As such, in some embodiments, theprocessor 312 (or the processing circuitry 310) may be said to causeeach of the operations described in connection with the beamformingcontrol module 300 in relation to adjustments to be made to antennaarrays to undertake the corresponding functionalities relating tobeamforming responsive to execution of instructions or algorithmsconfiguring the processor 312 (or processing circuitry 310) accordingly.For example, the instructions may include instructions for processing 3Dposition information of a moving receiving station (e.g., on theaircraft 100) along with 2D position information of fixed transmissionsites in order to instruct the antenna array 250 to form a traffic beamor control beam with a corresponding size in a direction that willfacilitate establishing a communication link between the movingreceiving station and one of the fixed transmission stations asdescribed herein.

In an exemplary embodiment, the memory 314 may include one or morenon-transitory memory devices such as, for example, volatile and/ornon-volatile memory that may be either fixed or removable. The memory314 may be configured to store information, data, applications,instructions or the like for enabling the processing circuitry 310 tocarry out various functions in accordance with example embodiments. Forexample, the memory 314 could be configured to buffer input data forprocessing by the processor 312. Additionally or alternatively, thememory 314 could be configured to store instructions for execution bythe processor 312. As yet another alternative, the memory 314 mayinclude one or more databases that may store a variety of data setsresponsive to input sensors and components. Among the contents of thememory 314, applications and/or instructions may be stored for executionby the processor 312 in order to carry out the functionality associatedwith each respective application/instruction. In some cases, theapplications may include instructions for providing inputs to controloperation of the beamforming control module 300 for directing theantenna assembly 250 to form a traffic beam or a control beam in aparticular direction, and of the corresponding appropriate size, asdescribed herein.

In an example embodiment, the memory 314 may store position informationsuch as, for example, fixed position information indicative of a fixedgeographic location of one or more base stations or dynamic positioninformation indicative of a three dimensional position of the aircraft100. The processing circuitry 310 may be configured to determine anexpected relative position of the aircraft 100 based on the fixedposition information and/or the dynamic position information and provideinformation to the antenna array 250 to direct formation or selection ofa beam based on the expected relative position of the aircraft 100 (orsimply based on the position information). In other words, theprocessing circuitry 310 may be configured to utilize informationindicative of the locations of aircraft to determine where to point abeam for establishing a communication link to the aircraft. Trackingalgorithms may be employed to track dynamic position changes and/orcalculate future positions based on current location and rate anddirection of movement of the aircraft 100 to facilitate keeping a beampointed on the aircraft 100. The beamforming control module 300 maytherefore (either directly or via the RRH 260) act as a control devicethat is configured to adjust characteristics of the antenna array 250 toform directionally steerable beams steered in the direction of theexpected relative position of the aircraft 100.

In an example embodiment, the dynamic position information may includelatitude and longitude coordinates and altitude to provide a position in3D space. In some cases, the dynamic position information may furtherinclude heading and speed so that calculations can be made to determine,based on current location in 3D space, and the heading and speed (andperhaps also rate of change of altitude), a future location of theaircraft 100 at some future time. In some cases, flight plan informationmay also be used for predictive purposes to either prepare assets forfuture beamforming actions that are likely to be needed, or to provideplanning for network asset management purposes. The dynamic positioninformation may be determined by any suitable method, or using anysuitable devices. For example, the dynamic position information may bedetermined using global positioning system (GPS) information onboard theaircraft 100, based on triangulation of aircraft position based on adirection from which a plurality of signals arrive at the aircraft 100from respective ones of the base stations, using aircraft altimeterinformation, using radar information, and/or the like, either alone orin combination with each other.

In some cases, the traffic channel beams 340 may, for example, haveazimuth and elevation angle widths of 5 degrees or less. Moreover, insome cases, the traffic channel beams 340 may have azimuth and elevationangle widths of 2 degrees or less. However, larger sized traffic channelbeams 340 may also be employed in some embodiments. Meanwhile, thecontrol channel beams 350 may have a width that is at least two to tentimes larger than the width of the traffic channel beams 340. Moreover,in some cases, the control channel beams 350 may have a width thatcovers the entire sector in which the corresponding control channel beam350 is formed.

The structure shown in FIG. 3 may be employed to generate steerablebeams in azimuth and/or elevation within sectors defined around a basestation. Moreover, example embodiments may form beams that areconfigured to have a relatively long range (e.g., greater than 100 km)and may be generally aimed just above the horizon. This ensures thatcommunications between base stations and aircraft are not conducted suchthat the aircraft communicates with ground stations nearby or below theaircraft. Such ground stations would tend to be located proximate tointerference sources that could also reach the aircraft. However, byfocusing long range beams from a base station toward the horizon to anaircraft, and by focusing beams similarly back toward the base stationfrom the aircraft, interference can be significantly reduced. Theresulting coverage areas or communication cells formed around the basestations therefore may have a wedge shape as the coverage areas extendaway from the base stations just above the horizon. In some cases, thesecoverage areas may further be defined by sectors. FIG. 4 illustrates aperspective view of coverage areas (e.g., sectors) generated by a basestation of an example embodiment.

The BS 110 of FIG. 4 employs a plurality of antenna elements that formthe antenna array 250 of FIG. 3. In the example of FIG. 4, six sectorsof thirty degrees each are shown, and the sectors cover about 180degrees around the BS 110. However, sectors could be formed to havedifferent sizes, and different numbers of sectors could be employed. Forexample, if the sectors were 60 degrees in width, as few as threesectors could duplicate the coverage area shown in FIG. 4. However, theBS 110 could also as many as twelve sectors in cases where thirty degreesectors are employed and 360 degrees of coverage is desired. The BS 110is configured to scan within each respective sector as configured bycontrol initiated by the beamforming control module 300.

The individual sectors (e.g., first sector 400, second sector 402, thirdsector 404, etc.) shown in FIG. 4 are supported by one physical radiosupplying wireless communication traffic and control data to theantennas of the BS 110. The radio may support LTE-based traffic andcontrol data in some cases, although modifications to such LTEcommunications may be effected to support ATG network communications.Each sector may be defined between azimuth boundaries and elevationangle boundaries. Thus, for example, one of the sectors may extendbetween a first azimuth 410 and a second azimuth 412 and between a firstelevation angle 420 and a second elevation angle 422. The width of theazimuth boundaries may determine the number of sectors that are neededto provide the desired amount of coverage around the BS 110.

The sectors are defined between two azimuths to define a triangular orpie shaped sector profile in the vertical plane, and are defined betweentwo elevation angles to define a wedge shaped profile in the verticalplane. Within each of the sectors, beam formation may occur to selectdesired beam formations to effectively provide for formation of asteerable beam that can be steered in both azimuth and elevation withinthe sector.

As discussed above, two separate RF chains may be provided so that thesteerable beams can have different sizes dependent upon the logicalchannel for which the beam is being generated. In this regard, for thesteerable beam may have azimuth and elevation widths of a first sizewhen the steerable beam is formed in connection with traffic channelbeams 340, and the steerable beam may have a second size when thesteerable beam is formed in connection with control channel beams 350.The second size may be larger than the first size. Thus, for example,the steerable beam may have azimuth and elevation widths as small asfive degrees, or even two degrees, to define the size of the steerablebeam when the steerable beam is formed via the first RF chain 325.However, the steerable beams may have larger sizes (e.g., two to tentimes larger) including being as large as the entire correspondingsector, when the steerable beam is generated as the control channelbeams 350 via the second RF chain 335.

In an example embodiment, the BS 110 employs channels having a frequencydetermined according to a channel band plan that promotes reduction ofinterference potential between neighboring BSs. Thus, for example, eachBS may have a 10 MHz channel designated for transmission and a separate10 MHz channel designated for receiving data transmitted by aircraft.Meanwhile, the separate set of paired 10 MHz channels for transmissionand receive that are assigned to the BS 110 may be different from thesame sized set of paired channels assigned to the second BS 130.Moreover, in an example embodiment, each adjacent BS to the BS 110 alonga same direction may have a different 10 MHz channel assignment fromeach other. Thus, for example, although the ATG network 200 couldoperate in any suitable spectrum, if the ATG network 200 operated in theunlicensed band, transmission channels for three sequential BSs may befrom 2.4078 GHz to 2.4178 GHz for transmission channel A, 2.4178 GHz to2.4278 GHz for transmission channel B, and 2.4278 GHz to 2.4378 GHz fortransmission channel C. Meanwhile, reception channels for the threesequential BSs may include 2.4457 GHz to 2.4557 GHz for receptionchannel A, 2.4557 GHz to 2.4657 GHz for reception channel B, and 2.4657GHz to 2.4757 GHz for reception channel C.

If BS 110 operates on channel A for transmission and reception, then thesecond BS 130 may operate on channel B, while the BS on the oppositeside of BS 110 from the second BS 130 would operate on channel C. Byrepeating this pattern in every direction, the BSs will always havefrequency separation relative to adjacent operating BSs. Thus, thepotential for inter-site interference while the aircraft 100 transitsits flight path is reduced. Meanwhile, the aircraft 100 will includeswitching circuitry to enable the aircraft 100 to switch between thecorresponding channels as the aircraft 100 transitions from cell tocell.

As an example, the aircraft 100 may be transitioning from BS 110 to thesecond BS 130. The aircraft 100 may be located at a bearing of 30degrees from the second BS 130 on an elevation angle of 6 degrees. Theaircraft 100 may send an access request on an uplink random accesschannel to the second BS 130 in a corresponding one of the sector wide,control channel beams 350. The second BS 130 may acknowledge therequest, while the aircraft 100 communicates its position data to thesecond BS 130. After the second BS 130 learns the position dataincluding, for example, location, velocity and heading of the aircraft100. With the position data, the second BS 130 may calculate the azimuthand elevation corresponding to the aircraft 100 and direct one of thetraffic channel beams 340 to be formed in an optimal pointing directionfor the aircraft 100. A telemetry cable may be provided, as alow-bit-rate data cable, for providing beam formation information to theantenna assembly 250, separately from the two separate RF chains.Although the two separate RF chains could feed respective differentantennas (or sets of antenna elements), in some cases the two separateRF chains could feed the same antenna (or set of antenna elements) andallow the antenna (or antenna elements) to function as two antennas eventhough they are physically a single structure.

Thus, a network for providing ATG wireless communication in variouscells in accordance with an example embodiment may include multiple basestations that each include an antenna array defining sectors havingrespective widths defined in azimuth, and a beamforming control module.The beamforming control module may be configured to communicate with theantenna array via a first RF chain to perform beamforming definingtraffic channel beams having a first width, and a second RF chain toperform beamforming defining control channel beams having a secondwidth. The second width may be greater than the first width.

The base station, beamforming control module and/or antenna arrays ofvarious examples may be modified, augmented or altered in various ways.For example, in some cases, the beamforming control module may beconfigured to generate the traffic channel beams and the control channelbeams simultaneously via the first and second RF chains, respectively.In some examples, the second width is substantially equal to a width ofeach sector. In some cases, the first width is about 2 degrees to about5 degrees in azimuth. Alternatively or additionally, the second widthmay be about two to ten times larger than the first width. In someexamples, each sector is about 30 degrees to about 60 degrees wide inazimuth. In an example embodiment, a remote radio head may be disposedproximate to the antenna array. In such examples, the remote radio headmay receive location information to enable the remote radio head toemploy the second RF chain to provide the traffic channel beams to anaircraft while tracking the aircraft. In some cases, all sectors of thebase station employ separate transmit and receive channels. In such anexample, the separate transmit and receive channels of the base stationmay be different than transmit and receive channels of each adjacentbase station of the network. Alternatively or additionally, the antennaarray may be fed by both the first and second RF chains to enable theantenna array to have one physical structure but functionally act as twodifferent antennas. In some embodiments, the first RF chain may be splitto supply two antennas serving a single control channel sector.

Accordingly, some example embodiments described herein may providearchitectures for improved ATG wireless communication performance. Inthis regard, some example embodiments may provide for base stationshaving antenna structures that facilitate providing wirelesscommunication coverage in vertical and horizontal directions withsufficient elevation to communicate with aircraft at high elevations.The base stations employ antenna technology that allows different sizedcontrol and traffic channels to be provided so that traffic channels cantrack aircraft transiting through the network.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Moreover, although the foregoing descriptions and the associateddrawings describe exemplary embodiments in the context of certainexemplary combinations of elements and/or functions, it should beappreciated that different combinations of elements and/or functions maybe provided by alternative embodiments without departing from the scopeof the appended claims. In this regard, for example, differentcombinations of elements and/or functions than those explicitlydescribed above are also contemplated as may be set forth in some of theappended claims. In cases where advantages, benefits or solutions toproblems are described herein, it should be appreciated that suchadvantages, benefits and/or solutions may be applicable to some exampleembodiments, but not necessarily all example embodiments. Thus, anyadvantages, benefits or solutions described herein should not be thoughtof as being critical, required or essential to all embodiments or tothat which is claimed herein. Although specific terms are employedherein, they are used in a generic and descriptive sense only and notfor purposes of limitation.

What is claimed is:
 1. A base station within a network for providingair-to-ground (ATG) wireless communication in various cells, the basestation comprising: an antenna array defining a plurality of wedgeshaped ATG communication sectors having respective widths defined inazimuth; a beamforming control module configured to communicate with theantenna array via a first RF chain to perform beamforming definingtraffic channel beams having a first width, and a second RF chain toperform beamforming defining control channel beams having a secondwidth, the second width being greater than the first width, and a remoteradio head disposed between the antenna array and the beamformingcontrol module, wherein the remote radio head receives locationinformation to enable the remote radio head to employ the first RF chainto provide the traffic channel beams to an aircraft while tracking theaircraft.
 2. The base station of claim 1, wherein the beamformingcontrol module is configured to generate the traffic channel beams andthe control channel beams simultaneously via the first and second RFchains, respectively.
 3. The base station of claim 1, wherein the secondwidth is substantially equal to a width of each ATG communicationsector.
 4. The base station of claim 3, wherein the first width is about2 degrees to about 5 degrees in azimuth.
 5. The base station of claim 1,wherein the second width is about two to ten times larger than the firstwidth.
 6. The base station of claim 1, wherein each ATG communicationsector is about 30 degrees to about 60 degrees wide in azimuth.
 7. Thebase station of claim 1, wherein all sectors of the base station employseparate transmit and receive channels.
 8. The base station of claim 7,wherein the separate transmit and receive channels of the base stationare different than transmit and receive channels of each adjacent basestation of the network.
 9. The base station of claim 1, wherein theantenna array is fed by both the first and second RF chains to enablethe antenna array to have one physical structure but functionally act astwo different antennas.
 10. The base station of claim 1, wherein theremote radio head is provided proximate to the antenna array at a topportion of a tower or mast associated with the base station.
 11. Anetwork for providing air-to-ground (ATG) wireless communication invarious cells, comprising: a first ATG base station having a firstantenna array defining a plurality of first sectors having respectivewidths defined in azimuth; and a second ATG base station having a secondantenna array defining a plurality of second sectors having respectivewidths defined in azimuth, wherein the first ATG base station and thesecond ATG base station are disposed offset from each other along afirst direction, wherein each of the first and second ATG base stationsincludes a beamforming control module configured to communicate with thefirst and second antenna arrays, respectively, via a first RF chain toperform beamforming defining traffic channel beams having a first width,and a second RF chain to perform beamforming defining control channelbeams having a second width, the second width being greater than thefirst width, wherein each of the first ATG base station and the secondATG base station comprises a remote radio head disposed between thebeamforming control module and the first and second antenna arrays, andwherein the remote radio head receives location information to enablethe remote radio head to employ the second RF chain to provide thetraffic channel beams to an aircraft while tracking the aircraft. 12.The network of claim 11, wherein the beamforming control module isconfigured to generate the traffic channel beams and the control channelbeams simultaneously via the first and second RF chains, respectively.13. The network of claim 11, wherein the second width is substantiallyequal to a width of each sector.
 14. The network of claim 13, whereinthe first width is about 2 degrees to about 5 degrees in azimuth. 15.The network of claim 11, wherein the second width is about two to tentimes larger than the first width.
 16. The network of claim 11, whereineach sector is about 30 degrees to about 60 degrees wide in azimuth. 17.The network of claim 11, wherein all sectors of the first and second ATGbase stations employ separate transmit and receive channels.
 18. Thenetwork of claim 17, wherein the separate transmit and receive channelsof the first ATG base station are different than transmit and receivechannels of the second ATG base station.
 19. The network of claim 11,wherein the antenna array is fed by both the first and second RF chainsto enable the first and second antenna arrays to each have one physicalstructure but functionally act as two different antennas.